The 12m Telescope

12M Telescope (EIE ALMA Protoype Antenna) - Kitt Peak

The Arizona Radio Observatory operates and maintains a 12 meter diameter telescope on Kitt Peak, 50 miles (80 km) WSW of Tucson, Arizona, for astronomical observations at millimeter wavelengths.

The ARO 12 Meter Telescope began as the 36 Foot Telescope, the telescope responsible for the birth of millimeter-wavelength molecular astronomy. During a period of explosive growth in this new area of astronomical research dozens of molecular species known to exist in the interstellar medium were first detected at the 36 Foot. In 1984, the telescope's reflecting surface and surface support structure were replaced and the 36 Foot was re-christened the 12 Meter. Subsequently, the scientific program has evolved from one dominated by observing programs in Astrochemistry to one with a broader mix of studies of molecular clouds and Galactic star formation, evolved stars, Astrochemistry, and external galaxies.

The 12m offers users flexibility and the opportunity to respond quickly to new scientific developments. The Observatory maintains low-noise receiving systems covering all atmospheric windows form 68 GHz to 180 GHz. Operational reliability throughout is emphasized. Flexible spectral line and continuum backends allow the observer to match the instrument to the scientific goals. The telescope control system offers great flexibility, efficiency, and convenience, and provides a proven remote observing capability.

During the period from April 2013 thru November 2014 the original 12 Meter telescope was retired and removed. It was replace by a Alma Prototype Antenna designed by ESO. The prototype was moved from it's location at the VLA to the Kitt Peak dome in late 2013 and was fully operational by November 2014.


Equipment Summary and Status - last updated August 11 2021

  • East Longitude: -111 36 53.475
  • North Latitude: +31 57 12.0
  • Elevation: 1914 meters (6280 feet)
  • Primary Reflector Diameter: 12.0 meters
  • Focal Ratio (f/D):
    • Prime Focus: 0.40
    • Secondary Focus: 8.0
  • Surface Accuracy: <60 um rms
  • Observing season: October - June
  • Carbon fiber construction
  • Altitude over Azimuth
  • Absolute pointing accuracy: 2.5” rms
  • Tracking precision: 0.2” rms
  • Efficiency: 85% +/- 5%
  • Azimuth range: +/-270°
  • Elevation range: 3° to 110°
    • Observational range: ~18° - 84°
  • Slew speed: 360° min-1
    • Observational value: 60° min-1 (Dome tracking limited)
  • Supports position-switching, beam-switching, on-the-fly mapping, and continuum observing

Front Ends

Multi - Band Receiver ( 4mm, 3mm, 2mm, 1mm, Dual polarization, SBS )

  • 3mm (ALMA Band 3; 84 – 116 GHz; Available)
    • Image Rejection: 15 dB minimum, ≥ 20 dB typical
    • Typical Tsys@90GHz = 120-160 K, Tsys@115GHz = 250-375 K
    • Best Tsys@90GHz = 85-110 K, Tsys@115GHz = 150-200 K
  • 4mm (66 – 90 GHz; Available, shared-risk)
  • 1mm (211 – 275 GHz; Available, shared-risk)
  • 2mm (In development)

Back Ends

ARO Wideband Spectrometer (AROWS)

The AROWS spectrometer at the 12m provides the capability of collecting spectral data over the entire output range of the receivers, or over portions of the receiver bandwidth at higher resolution.

AROWS has two working modes:

  • A wideband mode capable of processing a maximum of 4 GHz of bandwidth per window and up to 2 spectral windows.

  • A multi-window mode that has a maximum of 160 MHz bandwidth per window with up to 8 spectral windows.

For both modes, optionally a Hanning taper can applied as part of the digital processing. This reduces the frequency resolution from 1.2 to 2.0 times the channel spacing, but results in less aliasing and channels that statistically are more independent.

Also for both modes, output spectra can be reduced in size by selecting only the inner channels, with several options for the range.

Wideband mode

Up to two identical spectral windows may be placed anywhere in upper or lower sidebands of the receiver. The windows can be both in the same or in separate sidebands. Each window produces individual spectra for the H and V receiver polarizations. Thus, a total of up to four spectra will be produced. An example setup is shown in Figure 1. Table 1 shows the possible bandwidth and channel-spacing configurations for AROWS wideband mode.

Multi-window mode:

Up to eight spectral windows, presently restricted to the same size, may be placed anywhere in the upper or lower sideband of the receiver in groups of four. I.e. up to all eight windows in LSB or USB, or up to four in LSB and four in USB. Each window produces individual spectra for the H and V receiver polarizations. Thus, a total of up to sixteen spectra will be produced. Example setups are shown in Figure 2. Table 2 shows the possible bandwidth and channel spacing configurations for AROWS wideband mode.

 


Observing Restrictions

Sun Avoidance: The 12m requires a 10° Sun avoidance zone.


Recently Fixed and Current Issues

 


For more information, please contact:
Dr. Remo Tilanus, Operations Manager ARO
rtilanus@arizona.edu